Table of Contents:
- What is Radiant Flooring Heat?
- Difference Between Radiation Heat Transfer and Convection
- Modern Radiant Heat Systems
- Different Types of Radiant Floor Heating (RFH)
- Economical Hydronic Radiant Heat Installation
- Electric Radiant Floor Heating Systems
- Pros and Cons of Radiant Heat Systems
Your friends warmly extend an invitation to visit their brand new home. You’ve heard so much about it, and they’re thrilled to show it off. It’s in a wonderful location and, as you drive up, you’re taken with its stunning façade and striking landscaping. First impressions are lasting, and it’s already leaving a great one.
They answer the door, smiling. You gaze about, raving about the finishing. A great room concept with high vaulted ceilings and Palladian windows. A gorgeous chandelier. Wide baseboards and thick crown moldings. And those floors! Dark slate in the foyer and golden-hued hardwood throughout.
They take your coat, and you step out of your shoes, ready to take the tour. Then you stop. Something hits you as you stand on the stone, and then move in toward the hardwood floors. They’re so warm! Your friends keep smiling as they watch you react. Before you can ask, they answer for you. “It’s radiant floor heating.” You’re instantly sold on the warmth and start to consider installing a radiant heating system in your own home.
There is so much information available on the different types of radiant floor heat systems — so many options to choose from, so many products available and so many reasons why to use a radiant floor heating system. You might go online to take a look at your options. Maybe you visit a home show and talk to contractors about radiant heat home installation costs and the benefits of radiant floor heat.
It’s easy to get overwhelmed, though. You know why to use a radiant floor system, the advantages of radiant floor heating and have weighed the pros and cons of radiant heat. It’s getting the proper information on installing a radiant heating system in your home that can be difficult.
If this sounds familiar, then read on and find out about the different types of radiant floor heating systems, installing a radiant heating system in your home and how to enjoy the benefits of radiant floor heat.
What is Radiant Flooring Heat?
Radiant heat systems have been around since the days of the Romans when they laid a network of pipes under their marble floors and tied them into a hot water supply. Romans used a wood-fired boiler tended by slaves and an elementary pumping machine to circulate hot water that warmed their stone floors. In turn, the uniformity of the floor heat transferred heat to other articles in the rooms, including the human occupants.
Over the centuries, many other forms of radiant heat have taken shape as well. Some worked well, like the free-standing hot water radiators common in Victorian homes, and some have been colossal failures — like the electric radiant panels of the 1980’s that were built into ceilings and burned their structures to the ground.
Fireplaces and free-standing woodstoves are examples of radiant heat, and so are those unsightly electric baseboard heaters that bang up so many ankles. Other radiant heat devices have been commonly used like the kerosene floor units that were called “space heaters” and the little electric-powered ceramic boxes that still sit under desks and keep toes toasty.
But the best system of radiant home heat has always been the effective use of the home’s floors by using the broad bottom surface as an entire heating element. This lets the heat naturally rise and heat other objects by the scientific process of radiation.
Difference Between Radiation Heat Transfer and Convection
There’s a big difference between the heat transfer of radiation and the other common form of home heating — convection. Over the past century, the majority of homes in colder climates were heated by convection, rather than radiation. Convection is the process of heating air and blowing it about the rooms for the warm air to keep the floors, walls and ceilings heated. In turn, the objects in the room, like furniture and people, would stay warm by virtue of the air temperature.
These convection heaters are still widely used and are usually called “forced-air systems” — where there’s a central heating element in the furnace across which air is blown. This warmed air is then distributed about the home by a fan through “ductwork” and circulated back in a cooler state by other ducts called “cold-air returns.” The process repeats itself and is turned on and off by a pre-set thermostat. Fuel for these forced-air convection furnace systems is usually oil or natural gas, but some are electrically powered as well.
Radiant heat systems are increasingly popular, especially in the past quarter-century as technology has advanced, and the systems have proven themselves in reliability and economy. Unlike convection heating, radiant heat systems have no ductwork and no air circulation. Radiant systems depend on heat transfer by the infrared scientific principle used by the sun called “line of sight.” These invisible electromagnetic infrared waves radiate out from a warmed thermal mass. In a contained system like a house, the warmer objects naturally heat the cooler ones until a balance is achieved.
Modern Radiant Heat Systems
Today’s home radiant heat systems take full advantage of infrared radiation. By far, the most common source of a radiator in a home is the floor mass. Radiators can be locally located in one area like a bathroom floor or be installed across the entire sub-surface of the home’s floors. Other radiators are still used, such as wall-mounted panels or baseboard heaters — although ceiling radiators are almost always used in commercial applications like warehouses.
The reason for keeping the heat source low is simple. Heat rises, so it makes sense to locate the heat source at the floor level. This lets the warmth naturally travel through the “hot” zone, which is from a person’s toe to head area. All objects in the hot zone reach equilibrium in temperature after the radiant heat system has been operating for a while, including people. Gone is that rush of hot air when the furnace kicks in and that sudden shot of coolness when it shuts off.
The infrared principle of radiant floor heat is simple, and the reasons why to use a radiant floor heating system are clear. However, understanding the different types of radiant heating systems for your home and installing radiant heat in a house are a bit more complex.
Different Types of Radiant Floor Heating (RFH)
There are two main forms of radiant floor heating, or RFH as it’s known in the home heating business. One is hydronic where water or a specific fluid like glycol is warmed by some type of a fuel-fired boiler and is then circulated through a piping system under the floor surface. The second is by electric radiator panels where the electric wires or cables set under the floor are forced to resist current, which then generates heat.
These two forms of radiant floor heat are simple in concept. However, both systems have a vast array of different components for different applications as well as a variety of brand and specific installation requirements. One of the biggest considerations in choosing a particular form of radiant floor heat is whether the application is in new construction or if it’s being installed in a renovation.
Retrofit Radiant Heat Systems
For entire home installations, it’s difficult, if nearly impossible, to retrofit a radiant heat system in an existing house, especially a hydronic system. Localized radiant floor heat systems to be used in one or several rooms like bathrooms, kitchens or laundry rooms are easily renovated with electric radiant floor heat. This is much more cost-effective on a smaller scale. Larger renovations like additions to a home may be suitable for a larger scale and more expensive hydronic system.
Making a decision on which type of radiant floor heating system to use really depends on the application. First, it’s necessary to know how each type of radiant floor heat system works before deciding on installing radiant heat in a house.
Hydronic Radiant Floor Heating Systems
A hydronic or hot water radiant floor heating system is the most expensive of the two main RFH systems to purchase and install. That’s primarily due to the number of components and the amount of skilled labor necessary to build and install a hydronic RFH system.
A hydronic radiant floor heat system works by heating water or glycol in a boiler and pumping it through a maze of pipes installed under the floor or right within the floor surface itself. The heat from the hot water transfers to the floor mass and then radiates through thermal transfer to other articles with solid mass such as the walls, ceilings, furniture and people. It does not rely on heating or moving air to transfer warmth.
Hydronic floor heat is normally installed during new construction as the technical challenge of running the system under an existing floor during renovation is huge. It’s also far more economical in the long run to install a hydronic system throughout the entire house rather than dedicating it to smaller localized areas.
Economical Hydronic Radiant Heat Installation
The primary components of a hydronic radiant floor heating system are:
- The boiler — which is a metal tank containing a heating device, commonly called a burner. Hydronic tanks come in a range of fluid capacities dependent on the size of the home.
- The fluid — which is the liquid medium to be heated and circulated as the source of heat transfer. Normally, fresh tap water is all that’s used due to cost and availability. Some systems have a non- corrosive and non-freezing fluid like glycol.
- The fuel — which is required to be burned to produce energy that can be transferred to the fluid. Common fuel sources are natural gas, oil and electricity. Wood is sometimes used in rural areas where the supply is plentiful, and sometimes wood-fired boilers are backed up by an auxiliary electrical unit.
- The piping — which is woven throughout the floor as a distribution system. Metal pipes are rarely used due to long-term corrosive concerns. Virtually all hydronic radiant floor heat systems today use ½ inch diameter plastic tubing made from PEX or Cross-linked Polyethylene piping. PEX is highly flexible, won’t rust and comes in long lengths, which allow PEX pipe to be woven with minimal or no joints.
- The pump — which is required to pressurize the system and maintain a constant, low-velocity flow of warm fluid throughout the home. Most, if not all, pumps are electric.
- The manifold — which is a distribution center for the pipes allowing different zones of the home to be heated independently. This energy-saving feature lets the flow to certain areas of the home be turned down so unoccupied areas are cooler.
- The thermostat — which is the temperature control for the hydronic radiant floor heat system. Normally, each zone has an independent thermostat which is tied into the manifold. Programmable thermostats are often used as an energy saving device.
Aside from the components of a hydronic radiant floor heat system, there are three different methods of installing the distribution pipes:
- In-slab piping is set directly inside the floor and encased in concrete. This is common for basement floors or slab-on-grade construction and is best-suited for new construction. Rigid insulation is placed between the ground and the pipes and the concrete slab surface. A final floor finish is then placed on top of the slab. That might be ceramic tile, linoleum, laminates, carpet or engineered hardwood.
- In-screed piping is also encased in concrete although this application works in conjunction with an existing subsurface like another concrete slab or a wooden floor joist system. PEX piping is laid in a woven pattern, and then a thin, non-structural screed of specially-designed, light-weight concrete is poured over the pipes.
- Under-timber piping is where hydronic piping is set within a wooden floor joist system, underneath the wooded subsurface and final floor finish. This is normally used in a second or third-floor area and takes advantage of the floor joist cavities while avoiding the cost, weight and additional thickness of an in-screed concrete pour. To make an under-timber radiant floor heat hydronic system efficient, the joist areas are insulated with fiberglass batts, and foil reflectors are installed under the pipes to direct heat upward.
Electric Radiant Floor Heating Systems
The other common and popular form of radiant floor heating system is based on electric current resistance. This is much more suitable for isolating specific areas of a home such as bathrooms and kitchens as the cost of installing an electric system throughout an entire home would be prohibitive, not to mention the continual cost of operation.
Electric Radiant Floor Heating Systems
Electric radiant heating systems are best suited for wooden floor applications rather than installed over concrete slabs. Unless the slabs are very well insulated, the energy required from electric resistance can be so significant in heating the concrete mass that the economies of scale vanish.
Electric radiant floor heating systems lend themselves well to renovations, although they’re commonly used in new home construction. Electric systems come in a number of different applications and sophistication. Some are as simple as thin, electric mats. These are similar to an electric blanket that can be placed on the surface of an existing floor and plugged into a wall socket. Another mat or area rug is then set on top for aesthetics.
Other electric radiant floor heat devices are set right into the floor with another finished product placed above them. Ceramic tile is the most common material, followed by laminate flooring. Most of permanent electric radiant floor heating systems are designed for the specific application. A template is made and given to the supplier who designs the product for the exact size and shape of the area to be heated.
All electric radiant floor heat systems use the same principle of electric current resistance to create heat and then transfer it by thermal mass to the finished flooring. The heat then goes outward to surrounding objects. Not all electric radiant heat systems use the same approach in design or materials.
The most popular electric radiant floor heating systems are:
- Electric mats — These are wafer-thin pads or flexible blankets that contain a woven pattern of tiny resistance wires, typically nichrome or copper. These pads come in preexisting sizes for standard areas but are normally custom built for the exact area of installation. This can include precise angles, curves and pockets depending on the floor shape.
- Bare-wire cables — Bare-wire cables are supplied in a pre-measured roll to a specific length. These are fed through small plastic supports nailed to the floor and then encased in a thin skim of mortar.
- Insulated wire cables — Insulated cables also arrive in a prepared length, and then they are laid directly on the floor and cast in thin-set concrete.
Regardless of the type of electric radiant floor heating system, all are factory-built to remain in one piece and not cut, broken or altered. Any interference or interruption in the flow of electricity makes the system inoperable. This is one of the drawbacks to installing an electric radiant heat system. However, assuming they are installed correctly and properly taken care of, the likelihood of them having problems is small.
Electric radiant floor heating systems have fewer components than hydronic radiant heating systems. The parts in an electric radiant floor heat system are:
- The resistance wires — The electricity flows though these wires, is resisted and builds up heat. The size, length and design of the wires depend on the manufacturer and the specific application. Generally, smaller applications have smaller sized wires and are cheaper to purchase, install and operate.
- The mat or setting — This is what holds the resistance wires apart and keeps them evenly spaced. Mats are supplied with that type of pre-built system whereas cables or wires set on the floor are encased with a regular concrete mortar that is mixed and applied on the job site.
- The temperature probe — The temperature probe is normally set on the tail end of the wires and sends a signal back through the wires to the thermostat.
- The thermostat — This records the preset temperature and controls the electricity flow, adjusting the temperature to the room setting. Electric radiant floor heat system thermostats are connected by a separate wire to the cable or pad and are wall mounted. Some retrofit electric radiant heat systems have remote and programmable thermostats.
Pros and Cons of Radiant Heat Systems
If you’re still wondering why to use radiant floor heating systems, it’s important to explore the pros and cons of radiant heat. The advantages of radiant floor heating far outweigh the disadvantages, especially in radiant heat systems installed throughout the entire house during the initial construction. Installing radiant heat in your house is a major investment and must be viewed in long-term returns. This includes both hydronic and electric radiant floor heating systems.
Advantages of radiant floor heat systems include:
- Comfort — Undoubtedly, the biggest advantage of radiant floor heat is the uniform distribution of heat and the comfort it provides for the occupant. There are no hot and cold spots, and the even heat does not take away from the body’s natural heat.
- Economical — In the long-term, radiant floor heat costs less to operate once the initial capital investment is absorbed.
- Quiet — Radiant floor heat has no noise. There are no fans, rush of air or furnace growls to hear.
- Clean — With no moving air to distribute dust and airborne particles, radiant floor heat provides an exceptionally clean environment. It’s perfect for people with allergies or breathing difficulties.
- No ductwork — Whereas convection forced-air furnaces must work in conjunction with warm and cold air ducting, radiant systems are entirely contained in the floor. There are no boxed or drop ceilings to duck for or to try to disguise.
- Low maintenance — Radiant floor heat has few or no moving parts to service or break down. This includes filters to change and ductwork to clean.
- Better furniture placement — There are no floor or wall registers to contend with, making furniture placement more versatile.
When looking at the pros and cons of radiant heat, there are virtually no disadvantages to a radiant floor heat system other than the initial cost of installation. This is soon compensated for by having lower energy consumption and far more personal comfort.
Contact Bruni & Campisi to Install a Radiant Heating System
If you’re considering the installation of a radiant floor heating system or need services from a comprehensive provider of plumbing and HVAC systems, contact Bruni & Campisi. We’re the professionals you can rely on and trust for economic, eco-friendly solutions, including information on hydronic and electric radiant floor heating. Since 1979, we’ve served the needs of satisfied residential and commercial clients throughout Greenwich, CT, Stamford, CT, Westchester County, NY and the surrounding areas.
Our knowledgeable, attentive team is happy to answer all your questions. Contact us for a free estimate today.